The pathological features of FDG-PET negativity in patients with pancreatic ductal carcinoma

Abstract

Introduction: Usefulness of FDG-PET in pancreatic cancer various studies have been carried out. Aims: In this study, we clarified the pathological features of pancreatic ductal carcinoma with negative positron emission tomography(PET) findings and determined the factors that might affect fluorodexyglucose(FDG) accumulation by the pancreatic ductal carcinoma. Patients & methods: Eighteen patients with pancreatic ductal carcinoma and negative findings on PET preoperatively enrolled. Pathological findings (proliferation type and extent of fibrosis) and reproductive activity were examined. Proliferation was classified into 3 types: equal, extended, and collective. Reproductive activity was assessed using the Ki67 index; the Ki-67 indexes for 11 patients with positive PET findings were used as controls. Results: There were 10, 3, and 5 patients with equal, extended, and collective proliferation, respectively. Patients with equal and extended proliferation generally had massive fibrosis. The difference in proliferation type could not be determined by the Ki-67 index, which ranged from 2.7 to 12.6(average, 6.8). The average Ki-67 index of patients with PET positivity was 26.1(p<0.01) Conclusion: PET negativity can be defined by proliferation type; patients with equal and extended proliferation accounted for 72%(13/18) of the patients. These results suggest that low cell density, fibrosis, and extension cancer gland indicate a decrease in the amount of localized cancer cells. The decrease in the number cancer cells caused a reduction in FDG accumulation, which possibly lead to PET negativity. Patients with PET negativity had a lower rate of Ki-67 positivity than patients with PET positivity. It was hypothesized that the reproductive activity of the cancer cells also contributes to PET negativity.